[PATCH xserver 4/4] xwayland: sync event queue to check compositor reply

[Olivier Fourdan]

----- Original Message -----
> ----- Original Message -----
> > Read and dispatch pending Wayland events to make sure we do nto miss a
> > possible reply from the compositor prior to discard a key repeat.
> > 
> > Signed-off-by: Olivier Fourdan <ofourdan at redhat.com>
> > ---
> >  hw/xwayland/xwayland-input.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/hw/xwayland/xwayland-input.c b/hw/xwayland/xwayland-input.c
> > index 28d8b54..89f6faf 100644
> > --- a/hw/xwayland/xwayland-input.c
> > +++ b/hw/xwayland/xwayland-input.c
> > @@ -546,6 +546,9 @@ keyboard_check_repeat (DeviceIntPtr dev, XkbSrvInfoPtr
> > xkbi, unsigned key)
> >      struct xwl_screen *xwl_screen = xwl_seat->xwl_screen;
> >      struct wl_callback *callback;
> >  
> > +    /* Make sure we didn't miss a possible reply from the compositor */
> > +    xwl_sync_events (xwl_screen);
> > +
> 
> Unfortunately it still cause a deadlock apprently:
> 
> #0  0x00007fab4b6f93a0 in pthread_cond_wait@@GLIBC_2.3.2 () from
> /lib64/libpthread.so.0
> #1  0x00007fab4df3249b in read_events (display=0x17f7b80) at
> src/wayland-client.c:1326
> #2  wl_display_read_events (display=0x17f7b80) at src/wayland-client.c:1396
> #3  0x0000000000423e34 in xwl_read_events (xwl_screen=<optimized out>,
> xwl_screen=<optimized out>) at xwayland.c:465
> #4  0x0000000000424adf in xwl_sync_events
> (xwl_screen=xwl_screen at entry=0x17f7910) at xwayland.c:524
> #5  0x0000000000424e15 in keyboard_check_repeat (dev=<optimized out>,
> xkbi=<optimized out>, key=<optimized out>) at xwayland-input.c:536
> #6  0x0000000000525417 in AccessXRepeatKeyExpire (timer=<optimized out>,
> now=<optimized out>, arg=0x22c61f0) at xkbAccessX.c:321
> #7  0x000000000058b6c3 in DoTimer (timer=0x2923510, now=now at entry=3317763,
> prev=prev at entry=0x81f6f8 <timers>) at WaitFor.c:420
> #8  0x000000000058c36a in WaitForSomething
> (pClientsReady=pClientsReady at entry=0x17efab0) at WaitFor.c:291
> #9  0x00000000005572ee in Dispatch () at dispatch.c:359
> #10 0x000000000055b503 in dix_main (argc=10, argv=0x7ffca1cbd528,
> envp=<optimized out>) at main.c:300
> #11 0x00007fab4bfaa0c1 in __libc_start_main () from /lib64/libc.so.6
> #12 0x0000000000423599 in _start ()
> 
> And that will freeze both the Xwayland server and the compositor, so not
> good.

That is actually fixed with v2 of the patch #3 (ie call prepare_read() before read() to avoid the deadlock as Pekka pointed out on irc).

Cheers,
Olivier